I have a question!

I know sunshine is the answer right! well my house sets north to south and the back yard is to the north, I have a small porch on the north west corner of my house which you can not use in the afternoon.
So I built a small rased bed next to the foundation so I could plant soma sort of vine that would shade the porch, well this spring I found a freebee Tomato plant growing in the middle of it, I like free and I let it grow, it out produced all my other plants. Now for my question I just checked at 1:30 PM the bed started getting sun the temperature was about 85 F, by 3:00 the temperature was 104, around 5:00 the bed was in the shade and it was 116F, now that's only 3.5 hours sun but the tomato plants in that bed now are one foot taller than the rest and the came from the same seed packet,
The area the bed is in is only about five feet wide from foundation to six foot fence and the houses on both sides of mine are two story. PS  The freebee was a roma.

I think the proof is in the puddin', so to speak!  I think the real answer is "It depends". Sun is great in Ohio, where we do not get the intensity you do nor th temps.  You have a nice experiment showing you the way.

That said, many volunteers are just sturdier in general.  They get an early start....etc.